In recent years, various pneumatic grain conveying systems have been employed for conveying grain to and from a grain storage bin or the like. These prior pneumatic grain conveying systems typically employed a positive displacement blower for forcing air into a closed duct or pipe system. Grain to be conveyed was introduced into the piping downstream of the blower by means of a so-called airlock grain inlet or other grain infeed device, which fed the grain into the pipe system in such a manner that the grain was entrained by the air flowing through the pipe system and in such a manner that the pressurized air was not lost thus maintaining the conveying capacity of the pneumatic conveying system. Downstream from the grain inlet the piping system may be directed upwardly, for example, along the sidewall of a grain bin, and along the sloped, conical grain bin roof to a center grain inlet opening in the roof, where a so-called deadhead deflector or a cyclone diffuser was positioned so as to allow the pressurized air to be vented to the atmosphere and to direct the grain into the grain inlet in the grain bin roof. Such pneumatic grain conveying systems have the advantage of moving the grain within a cushion of air that minimizes damage to the grain, as compared to mechanical grain auger conveyors or other types of mechanical grain conveying systems.
However, such pneumatic grain conveying systems, especially such pneumatic grain conveying systems having high capacity (e.g., 2,500 bushels/hour), require a powerful electric motor (e.g., up to 75 horsepower) for powering the positive displacement blower. Such motors are expensive. It is thus desirable to utilize the same motor and the same airlock grain infeed unit to convey grain to a plurality of grain storage bins. Heretofore, this has been accomplished by providing separate piping systems from the air lock to the various grain storage bins with a complex manifold/distributor, such as shown in FIG. 2 of the instant drawings and as will be hereinafter described, so as to permit the pressurized air duct from the grain infeed airlock to be selectively connected in an air tight fashion to a desired or selected piping system for a selected one of the plurality of grain storage bins. Not only did this prior manner of connecting the pressurized air conveying system to the piping system for a selected grain storage bin require the complex manifold/distributor, but it also required separate piping runs from the grain inlet airlock to each of the grain storage bins with each of these piping runs having a horizontal run along the ground and a vertical run along the vertical sidewall and conical roof of each bin. In turn, this added to the expense and complexity of such prior pneumatic conveying systems. These multiple runs of piping along the ground often interfered with vehicles which require close access to the grain bins. Still further, it has been found that such manifold/distributor systems are sometimes difficult to operate and they often require that the blower and airlock infeed be shut down while making a change from conveying to one bin and then to another bin.